In the invention disclosed in Japanese Patent Application Publication No. H06-64248, for example, the printing system switches the printing mode of the printing unit between a color printing mode and a monochrome printing mode. Specifically, the printing system prints one copy (an original) in color and prints the remaining copies (duplicates) in monochrome (i.e., restricts color printing).
Normally in color printing, an image is formed based on image data by superimposing toner or ink in the four colors cyan, magenta, yellow, and black on a recording medium. In monochrome printing, the image is formed based on the image data by applying toner or ink of the single color black on the recording medium. Since there is generally no need to superimpose toner or ink in the monochrome printing, the black toner or ink being applied in one layer on the recording medium, the monochrome printing is less expensive than color printing.